Plackett-burman design for determining the preference ofRhizomucor mieheilipase for FA in acidolysis reactions with coconut oil

Enzymatic preparation of structured oils containing short-chain fatty acids

Structured oils prepared by enzymatic transacylation with triacylglycerols (TAGs) and various fatty acids (FAs) were characterized. Transacylation with trilaurin and saturated FAs (C4:0-C16:0) was performed using Lipozyme RM-IM under standard reaction conditions. The structured oils thus produced had transacylation ratios of 25-37%, as medium-chain FAs > long-chain FAs > short-chain FAs. This result confirmed that short-chain FAs have little reactivity in enzymatic transacylation. All prepared oils shared the same composition of TAG molecular species, as demonstrated by HPLC analysis, and contained a mixture of mono-substituted, di-substituted, and non-substituted TAGs. The reaction conditions for transacylation with TAGs and short-chain FAs were optimized to improve transacylation ratios. The introduction ratios of C4:0, C5:0, and C6:0 into trilaurin were increased to 52.4, 42.5, and 34.1%, respectively, by extending the reaction time. Transacylation between TAGs and short-chain FAs was further examined by using Lipase PL. C4:0 was introduced at 51.1%, the same ratio as for Lipozyme RM-IM. When C5:0 and C6:0 were used as the FA substrate, the transacylation ratios obtained were 47.7 and 43.4%, respectively, higher than those for Lipase RM-IM. Lipase PL is therefore useful for introducing short-chain FAs into TAGs.

Lipase specificity in the transacylation of triacylglycerin

The Lipase-catalyzed transesterification method is utilized as a safe and effective method for preparing various structured oils. As each lipase shows different fatty acid specificity, it is important to select an appropriate lipase according to fatty acid species incorporated into oils. In the present study fatty acid specificities of lipases obtained from different origins were evaluated by transacylation between oils and various fatty acids. Of 12 kinds of lipases used, 5 lipases have 1,3-regio specificity and 7 lipases have non-regio specificity for hydrolysis of oils. Fatty acid substrates of transacylation were 8 saturated fatty acids with 6 to 18 carbon numbers, and C18 unsaturated fatty acids with different double bonds such as oleic, linoleic and linolenic acids. As results shown below, most lipases used gave high transacylation ratios for lauric acid when saturated fatty acids are compared and a different tendency in C18 unsaturated fatty acids. Regarding the fatty acid specificity of different lipases, fatty acid specificity of each lipase differed by its origin. Almost all lipases with or without regio specificities showed high selectivity for C10 and C12, especially C12 saturated fatty acid, and a little selectivity for C14-20 saturated fatty acids. On the other hand, C6 saturated fatty acid was little incorporated into TAG, and C18 fatty acids with higher unsaturation were incorporated easily into TAG. Transacylation activity defined as an acydolysis unit (AU) of an activity which is able to incorporate 1 micromol of C12 saturated fatty acid into TAG for 24h represents high relationship with the known hydrolysis activity. It is considered that structured lipids can be prepared effectively by transacylation based on the proper selection of lipase with higher transacylation or hydrolysis activities for specific fatty acids.